| The large deformation of soft rock tunnel with high geo-stress has been a difficult problem in the field of tunnel engineering. Nowdays, along with the development of high-speed railway and highway, long and deep tunnels emerge in large numbers. The large deformation problem is becoming even more prominent. Taking Daliang tunnel on the Lanzhou-Xinjiang second railway as project background. Use the means of theoretical analysis, numerical calculation and field test. The reasonable construction method si discussed, and the deformation controlling measures for large deformation of soft rock tunnel is researched. The main work and conclusions of the thesis are as follows:1. The mechanism and types of large deformation of soft rock is discussed, failure mode and deformation characteristics of squeezing deformation of soft rock tunnel under high geo-stress condition are analyzed. The surrounding rock squeezing degree is identified and the large deformation grade is divided based on Daliang tunnel construction practice. The main reasons for the large deformation during its construction are analyzed. Vertical deformation of tunnel vault and horizontal displacement of the tunnel well under the four methods are obtained.2. Three-dimensional numerical models are established according to the geological condition of large deformation area in the inclined shaft of Dalinag tunnel. Four Excavation method are simulated by FLAC3D, including three-bench method, three-bench method with temporary invert, three-bench seven-step method and CRD method. Select three-bench method with temporary invert as the preferred method in large deformation area of Dalinag tunnel, considering the construction factors and simulation results.3. Put forward the principle and measures to control the large deformation. To discuss the application of both the rock bolt and the advanced small pipe grouting in the large deformation tunnel, the effects of both bolt and the advanced small pipe grouting are simulated. The influence of different parameters on the deformation of tunnel is obtained. Calculation results showed that optimum length of rock bolt in Daliang tunnel is from 6m to 9m and the advanced small pipe grouting can give full play to its effect in use of 7m of it in the 140 degrees of tunnel arch. Evaluate the effect of a new type yielding bolt used in Daliang tunnel.4. Based on the in-situ monitoring data, the deformation of the tunnel, the surrounding rock pressure, the stress of steel arch, the depth of surrounding rock loose circle have been analyzed. It is demonstrated that the measures adopted in the Daliang tunnel have achieved good results, the deformation of the tunnel can be reduced by about 30% with those measures. |
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